Biology

Life as we know it is a wonderfully diverse enterprise. Organisms pass traits from parent to offspring, function in a varied and changing environment, and carry out a myriad of complex biochemical processes. Understanding the principles of biology helps give context and clarity to larger scientific and social issues. Our biology learning modules reveal the current state of scientific understanding on topics like cell structure and function, genetics, taxonomy, evolution by natural selection, and more.

Our bodies are efficient chemical processing plants, breaking down nutrients to use and store for energy. This module introduces carbohydrates, an important macronutrient. It explains how different carbohydrates are used by plants and animals. Simple sugars and complex carbohydrates are identified, and their biochemical structures are compared and contrasted.


This module provides an introdcution to the concepts of fats and proteins. The basic chemical structure of fats as triglycerides is reviewed, and an introduction to protein structure, including the peptide bond is given.


The cell is the basic structural unit of life. This module discusses the different types of cells that exist and the structures they are composed of. It also explores the relationship between cell structure and function. A brief history of modern cell theory is provided.


Evolution isn't always about competition. It can also be about cooperation, as is the case with the development of chloroplasts and mitochondria from free-living bacteria. This module explains the theory of endosymbiosis along with its origins. Convincing evidence in support of the theory is presented. The evolution of the nucleus and other organelles through invagination of the cell membrane is also discussed.


Cell division is an enormously complex process that must go on millions and millions of times during the life of an organism. This module explains the difference between binary fission and the cell division cycle. The stages of cell division are explored, and research that contributed to our understanding of the process is described.


In order for many medicines to work, the chemicals must move from the outside environment into the body. This module discusses the different mechanisms by which chemicals cross the cell membrane and the factors that influence this process. In addition to introducing biological absorption, the module explains how chemicals are stored and distributed within the body.


Through photosynthesis, plants harvest energy from the sun to produce oxygen and sugar, the basic energy source for all living things. This module introduces photosynthesis, beginning with experiments leading to its discovery. The stages of photosynthesis are explained. Topics include the role of chlorophyll, the action spectrum of photosynthesis, the wavelengths of light that drive photosynthesis, light-harvesting complexes, and the electron transport chain.


The experiences and observations of Charles Darwin significantly contributed to his theory of evolution through natural selection. This module explores those influences and describes evolution as a force for biological change and diversification. The first in a series, it details how the theory challenged the cultural mindset of the time, including the effect of his major works: On the Origin of Species by Means of Natural Selection and Sexual Selection and the Descent of Man.


The second in a series discussing the work of Charles Darwin, this module takes a deeper look into the processes that led to Darwin's theory of natural selection and examines specific mechanisms that drive evolutionary change. Key points on which the idea of natural selection rests are outlined. Examples from Darwin's personal life shed light on his thinking about change within a species and the "struggle for existence."


Our understanding of the term evolution has changed significantly since Darwin's time. This module explains how Darwin's work helped to give evolution the meaning it has today. It details the concept of "descent with modification" that Darwin described with the one figure originally included in Origin of Species. The module discusses how this model revolutionized scientific thinking about the similarities and differences between and within species, laying the foundation for our current understanding of biodiversity.


This module introduces the concept of evolutionary adaptation. It follows the development of Charles Darwin's ideas on how species adapt to their environment in order to survive and reproduce. The difference between adaptation and natural selection is explained. With a look at penguins and other examples from nature, the module explores the processes that influence the diversity of life.


This is the first in a series of modules that introduce species taxonomy. This module introduces Carolus Linnaeus' work.


This module discusses how taxonomic names for the genus and species categories are formed and standardized, and how the rules are bent when it comes to famous beasts, such as well known dinosaurs.


Inheritance patterns have been of interest since ancient times, but it was Gregor Mendel's work in the mid-1800s that confirmed that traits are passed on by two parents in a predictable pattern. This module describes the experiments that resulted in Mendel's Laws of Inheritance. A look at specific traits in pea plants over generations shows how Mendel's research methods resulted in an understanding of dominant and recessive genes. Partial dominance is also discussed.


This module is the second in a series and provides details on Mendel's work with dihybrid crosses and independent assortment.


This is the first in a series of modules that discusses the discovery, structure, and function of DNA. This module focuses on the identification of DNA as the genetic material through early experiments by Fleming, and Avery, MacLeod, and McCarty.


Exploration of the structure of DNA sheds light on fascinating properties of the molecule. This module, the second in a series, highlights major discoveries, from the parts of a nucleotide - the building blocks of DNA - to the double helix structure of the DNA molecule. The module describes scientific developments that led to an understanding of the mechanism by which DNA replicates itself.


In the field of molecular biology, scientists examine how DNA encodes all the complexities of living things. This third module in the DNA series focuses in the process by which DNA is replicated. The module describes the DNA synthesis assay, where scientists were able to replicate DNA in a test tube. Advancements in understanding the features and properties of DNA replication are discussed.


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